The present invention relates to screw stoppers in which the screw thread of the bottle neck terminates in a transverse projection forming a positioning stop for a corresponding projection of the screw thread of the stopper, which also comprises a second projection locked behind the stop of the neck. The passage of this second projection over the stop shoulder of the neck requires a certain elasticity of the stopper, failing which said second projection is rapidly destroyed. For decorative purposes, the prior art stoppers are made of plastic material coated with a metal cap which renders the stoppers undeformable. This results in the use of the stopper device described hereinabove being impossible.
It is an object of the invention to remedy this drawback both for stoppers covered with a rigid cap and for those whose plastic walls are too thick to obtain sufficient elasticity.